[FRAME] Run benchmark tests with real Runtimes

[ggwpez]

Currently we run the benchmark tests only with mocked runtimes. This necessitates an additional CI check that does a bench run with the actual runtimes.
Now with the genesis builder API we can extend the auto generated benchmark tests to also run with the real runtimes. Could be done as part of the define_benchmarks! macro in the runtime.

Depends on #3512 (dont want merge conflicts with that).

[ntn-x2]

I was just trying to implement the same thing for our runtimes, and found myself down a rabbit hole. So I 100% agree this is definitely a nice thing to have.